If you're using metal reels, a 120 reel will not hold a 220 roll. There are special 220 reels that were made for that size roll. Some fit in a standard metal tank, and some required a larger tank that was specially made for them (the reel was bigger in diameter than a standard tank).
If you use plastic reels, most of them, when adjusted for 120 film will also take a full-length 220 roll too. I know for sure that Paterson reels work this way, as Sarcophilus Harrisii said in his post.